A nanochannel typically has a round or square cross-section with a width, side, etc. of about 50 nanometers (nm) to about 100 nm, and a length of from about 1 micrometer (μm) to about 5 μm. See, for example, W. Reisner et al., “DNA confinement in nanochannels: physics and biological applications,” Reports on Progress in Physics 75, 106601 (September 2012) (hereinafter “Reisner”).
A nanochannel can provide a platform to study molecular behaviors at the single molecule scale. Namely, the nanochannel can sort, manipulate, and detect the DNA samples. See, for example, Reisner and J. Han et al., “Entropic Trapping and Escape of Long DNA Molecules at Submicron Size Constriction,” Physical Review Letters 83, 1688-1691 (August 1999) (hereinafter “Han”). As described in Han, an electric field is used to drive passage of DNA molecules through a microfabricated channel. With the process described in Han, however, the electric field will decay a distance 1/r away from the entry of the channel (wherein r is the radius of cross-section of channel) thereby limiting its utility.
Previously, different methods have been proposed to enhance the translocations of DNA for nanofluidic systems, such as a salt gradient and high voltages. See, for example, M. Wanunu et al., “Electrostatic focusing of unlabelled DNA into nanoscale pores using a salt gradient,” Nature Nanotechnology 5, 160-165 (2010) (published December 2009). These methods however only change the electric field distribution close to the nanoscale pore entry.
Thus, techniques which expand the electric field of entry into a nanochannel and thereby increase the capture zone and capture rate of the nanochannel for processes such as DNA sequencing would be desirable.